1. Field of the Invention
The invention generally relates to atrial ablation procedures. More particularly, the invention relates to an intra-esophageal balloon system that is configured to move a patient's esophagus away from an ablation site to prevent accidental damage to the esophagus during the performance of an ablation.
2. Discussion of the Related Art
Atrial fibrillation is the most common human arrhythmia. The incidence of atrial fibrillation increases with the age of the patient, and thus, the incidence of atrial fibrillation is becoming more prevalent as the average lifespan continue to increase. Atrial fibrillation is associated with increased morbidity and mortality and, in particular, a general decrease in quality of life for those afflicted with atrial fibrillation. Patients are at an increased risk of stroke unless they are treated adequately with anticoagulants. Anticoagulant treatment however, increases a patient's risk of bleeding, which carries with it its own set of dangers. Medications currently available for treating atrial fibrillation have proven to be only moderately effective in decreasing the incidence of recurrent atrial fibrillation, and these mediations do not decrease the patient's risk of having a stroke.
One method of treating atrial fibrillation has been to perform ablation of selected areas of the left atrium. There is evidence to suggest that ablating these areas of the left atrium serves to cure or prevent further incidences of atrial fibrillation, which thereby has shown to reduce the risk of stroke and reduce the necessity of anticoagulant therapy. Typically, ablations of this type are carried out via an intravascular catheter using radiofrequency or microwave energy to cause thermal damage to the selected parts of the left atrial tissue.
The posterior wall of the left atrium is particularly targeted for ablation because the pulmonary veins enter the atrium at this area of the left atrium. Thus, encircling the pulmonary veins with continuous rings of lesions is common in this procedure. The esophagus may however, be positioned so as to overlie one or more of these veins, thereby making the desired encirclement difficult or impossible. A significant and lethal complication of atrial fibrillation ablation is the accidental creation of an atrio-esophageal fistula following the development of lesions on the posterior wall of the left atrium. Because the esophagus is generally closely positioned to the posterior wall of the left atrium, thermal injury may be communicated to the esophageal wall resulting in disruption of the wall and formation of the atrio-esophageal fistula.
In addition to the foregoing, fractionated electrograms and vagal plexi are also frequently present on the posterior wall of the left atrium. These are also common targets of atrial fibrillation ablation. Again, the location of the esophagus may hinder application of a sufficient energy to successfully ablate enough tissue of the left atrium to prevent recurrence of atrial fibrillation. Further, the esophagus is a mobile structure. Thus, peristaltic movements thereof may cause the esophagus to move and change its position relative to the left atrium. Advanced intracardiac ultrasound systems that are used to locate the esophagus to prevent accidental damage thereto are often incapable of accounting for or tracking such movements, thus rendering these relatively complex and expensive systems ineffective. Fluoroscopic evaluation of the esophagus is also used to determine the position of the esophagus during ablation procedures like this however; such methods provide only two-dimensional information and thus may lead to misreading of the position of the esophagus as it relates to the left atrium.
In addition to the foregoing disadvantages, left atrial ablation of this kind also experiences a great deal of unwanted heat dissipation from the ablation catheter tip. Upon application of the catheter tip to the ablation site, the tissue immediately contiguous to the tip is heated, thereby disrupting cellular function thereof. A sufficient amount of heat must be generated to coagulate and denature the proteins in the myocardial cells. If a heat sink is present in close approximation of the ablation site, generating sufficient heat becomes difficult if not impossible using presently available RF generators. For instance, arteries in close approximation to the ablation site experience rapid blood flow sufficient to conduct heat away from the area rapidly.
Other methods, such as cryoablation and high frequency ultrasound, are still considered experimental and are associated with particular disadvantages specific to these types of ablation.
It has recently been discovered that successful atrial fibrillation ablation may require the introduction of lesions near the location of the inferior right pulmonary vein, which is located in close proximity to the phrenic nerve. Thus, it is has become more common for accidental injury to the phrenic nerve to occur. The phrenic nerve is responsible for operation of the diaphragm, and thus, injury to the phrenic nerve can be quite catastrophic. Thus a method or system for preventing such injuries is deemed highly desirable.
The need therefore exists to provide a device for carrying out atrial fibrillation ablation of the left atrium that does not suffer from the foregoing disadvantages. In particular, a device for moving the esophagus away from the left atrium of the heart is desired.